Hey all, I'm having some difficulty with my project:
We measure a lot of data per second, so we had to compromise by sending a
long list to the API, and then having the API create serveral objects:
The data coming in from request.data looks like this:
{
"datasource": "<serial number>",
"parameters": ["param_name_1", "param_name_2", "param_name_3" //(... Up to
100)],
"data_array": {
"time": ["time_stamp_1", "time_stamp_2", "time_stamp_3" //(... Up to 100)],
"values": [param_value_1, param_value_1, param_value_1 //(... Up to 100)]
}
}
Now, the model looks a little different, where I now have to "parse" the
above lists into the following model:
class Data(models.Model):
time = models.DateTimeField(db_index=True)
sensor = models.ForeignKey(Sensor, on_delete=models.CASCADE)
parameter = models.ForeignKey(Parameter, on_delete=models.CASCADE)
parameter_value = models.FloatField()
So, for clarity's sake, using the above example, I have to create 3
different objects:
Object 1 =
time = time_stamp_1
sensor = <serial number>
parameter = param_name_1
parameter_value = param_value_1
Object 2 =
time = time_stamp_2
sensor = <serial number>
parameter = param_name_2
parameter_value = param_value_2
Object 3 =
time = time_stamp_3
sensor = <serial number>
parameter = param_name_3
parameter_value = param_value_3
Now I thought, easy, I'll create a loop inside the create function!
Just in case: this is my serializers.py:
class DataCreateSerializer(ModelSerializer):
class Meta:
model = Data
fields = [
'id',
'time',
'sensor',
'parameter',
'parameter_value'
]
On my views.py I thought I could just override the create like so:
class DataCreateAPIView(CreateAPIView):
queryset = Data.objects.all()
queryset = queryset.prefetch_related('sensor', 'parameter')
serializer_class = DataCreateSerializer(queryset, many=True)
permission_classes = [IsSensor]
def create(self, request, *args, **kwargs):
try:
sensor = Sensor.objects.get(serial_number=request.data[
"datasource"])
# request.data["datasource"] = sensor.id
except:
print("Sensor serial number " + str(request.data["datasource"])
+ " not registered.")
dataDict = dict(request.data) # Turn data into dict, to get inner
lists
parameters = dataDict["parameters"] # Break down my dict into lists
time_stamps = dataDict["data_array"]["time"] # Break down my dict
into lists
values = dataDict["data_array"]["values"] # Break down my dict into
lists
for param, time, value in zip(parameters, time_stamps, values): #
Zip lists into one list for each index value. They will always correspond.
parameter = Parameter.objects.get_or_create(parameter_name=param
, parameter_position="None")[0]
request.data.update({
"sensor": sensor.id,
"parameter": parameter.id,
"parameter_value": value,
"time": time
})
serializer = DataCreateSerializer(data=request.data)
if serializer.is_valid():
serializer.save()
return Response(serializer.data)
return Response(serializer.errors)
The first "try..except" is just validation to check whether that sensor
exists in our DB.
Then I thought, get the request.data, break that down into lists, and then
zip() those lists into the objects that I need, and do the serializer.save
inside the loop, so it happens as many times as there are elements in the
list.
There will always be the same amount of items in each of the lists, if
there are 100 parameters, there will be 100 time stamps, and there will be
100 parameter values. So looping over the lists seems simple enough.
The problem seems to be that it stops at the first one. The line "return
Response(serializer.data)" seems to be exiting the for loop entirely, so it
doesn't go back and create another object with the next zipped item on the
list.
At this point I've been googling for a few hours and trying different
things, but nothing seems to work so far.
Any pointers? I can provide other models, views, or URLs if needed.
For clarification, the above code works, ONLY on the first object created,
it doesn't go back in the loop and creates the second or third.
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